It is well known in the field of sorting and packaging fruits, vegetables, tubers, and the like to employ photoelectric devices to accomplish the task of sorting the articles into like size groupings. One such device for accomplishing the sorting is disclosed in U.S. Pat. No. 3,774,040, issued on Nov. 20, 1973 to Stephen P. Stephanos.
These devices generally include a plurality of sorting heads, each head being provided with at least one horizontal and one vertical photoelectric sensor. Each sorting head requires its own associated circuitry, and the multiplicity of sorting heads and circuits is a major cost factor. Also, setting up and maintaining such a system of individual units is difficult.
Further, the vertically disposed photoelectric sensor includes at least one element, whether light source or sensor, which is disposed subjacent to the article conveyor. This subjacent element tends to accumulate dirt and debris, especially from freshly washed fruit, which interferes with the light beam and disrupts and accurate measuring and sorting of the articles. Some operators have resorted to using compressed air to blow away the dirt and debris, but this technique represents a substantial additional cost.
The horizontally disposed photoelectric sensors are used to determine the width (height) of the articles. Each of the multitude of sorting heads must be adjusted so that the horizontal sensor is disposed at the correct height above the conveyor, so that articles may be correctly sorted as to width as well as length. This manner of adjustment is arduous, and difficult to alter when the size categories must be changed.
Also, the multiple sorting head approach is utilized most effectively when the heads are set up to select articles of successively increasing or decreasing length. Due to the fact that the width selection is usually a binary choice, and due to selection errors caused by the articles being spaced too close together, many lots of articles must be sent through the sorting apparatus more than once to properly sort the articles into all the correct categories. This is an extravagance that is rarely affordable.